Stopper and plunger rod for a pre-filled syringe

ABSTRACT

A plunger rod adapted for attachment with a stopper for use with a syringe barrel is disclosed. The plunger rod includes an elongated member having a front end and a back end, the plunger rod extending along a longitudinal axis. The plunger rod includes at least one deflecting arm associated with the front end of the elongated member. The deflecting arm is capable of deflecting radially inward during insertion of the plunger rod into a stopper, and deflecting outward into contact with an inner surface of the stopper after insertion to lock the plunger rod within the stopper.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/941,851, filed Jun. 4, 2007, entitled “Stopper and Plunger Rodfor a Pre-Filled Syringe” and to U.S. Provisional Patent Application No.60/950,741, filed Jul. 19, 2007, entitled “Positive Displacement Stopperfor a Pre-Filled Syringe”, the entire disclosures of each of which arehereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a stopper assembly for use with asyringe and, more particularly, to a stopper assembly having a positivedisplacement feature for use with a pre-filled syringe such as thoseused in flush applications. The invention also relates to a plunger rodand an attachment member adapted for attachment with a stopper assembly.

2. Description of Related Art

Pre-filled syringes, such as those used in flush applications, aretypically filled with a saline solution and are used to flush catheters.Example pre-filled syringes are shown in U.S. Pat. Nos. 6,361,524 and6,743,216, which are incorporated herein by reference and which aredirected to syringe assemblies for flush applications. At the end of theflushing procedure, the nurse or technician bottoms out the stopper inthe syringe barrel. The process of bottoming the stopper in the barrelcan cause a phenomenon known as reflux. Reflux is the reversal of fluidflow up through the catheter, usually due to the spring back of thestopper at the end of a flush injection. This occurs because the stoppercompresses to force out additional saline, and subsequently springs backto shape. This causes the syringe to pull saline back into the syringe.This reflux can also pull blood back into the catheter, clogging it.This phenomenon of reflux is detrimental to the maintenance of thecatheter line. Accordingly, it is desirable to reduce or eliminatereflux within the syringe.

Existing stopper designs typically include a constant diameter seal anda constant stopper-to-barrel interference to create a seal that willprevent fluid housed inside the barrel from leaking past the front sealof the stopper. The contact pressure of the seal is determined by theinterference in these designs, and has to be sufficiently high enoughsuch that they will not leak under the highest possible fluid pressureinside the barrel. The disadvantage of this traditional design is thatthe higher contact pressures lead to higher static and dynamicfrictional forces. Static friction is commonly referred to as breakloose force. Additionally, these existing stoppers typically include tipdesigns that are not self-centering. Because the tips are notself-centering, they do not form a positive seal with the inside back ofthe luer taper when subjected to axial forces.

Existing stopper designs have attempted to prevent the flow of fluidfrom the catheter back into the syringe when the clinician does not usea recommended positive pressure flushing technique, and release theforce from the plunger rod prior to clamping the catheter. As discussedabove, blood entering back into the distal catheter lumen is known asreflux and this reflux can lead to clogged catheters. These previousdesigns focused on preventing spring-back of the stopper that wouldcreate a vacuum to draw fluid back into the syringe. These designs,while effective in reducing reflux, do not consistently prevent allreflux from occurring.

Pre-filled syringes are typically manufactured in an automated process.The process of manufacturing these pre-filled syringes includes thesteps of molding the syringe barrel, attaching the cap, filling thebarrel, inserting the stopper, sterilizing the filled syringe, theninserting the plunger rod. Because the filled syringes are typicallysterilized in an autoclave, size of the syringe is an issue. For thisreason, the syringe is typically sterilized prior to the insertion ofthe plunger rod. Commonly used plunger rods are those of a snap-fitdesign, attached to the stopper prior to inserting the stopper into thebarrel, or a threaded design, attached to the stopper after the stopperhas been inserted into the barrel. Plunger rods assembled into thestopper after the stopper has been inserted into the barrel require asignificant amount of force to be applied thereto during insertion.Axial forces applied to the plunger rod can cause the rod to becomedislodged from the stopper, be misaligned, and/or break. Additionally,currently used snap-fit and/or threaded plunger rods occasionally becomedislodged from the stopper during use.

Traditional plunger rods are typically cylindrical members, which areformed from a molded material. These known rods may have a ridgedsurface wherein four ribs, positioned 90° degrees with respect to oneanother, form the ridged surface. In this current four ribbed design, auser may apply a side load during flushing or aspiration that may benormal to the edge of the rib, causing minimal side loading deflection,or normal to the region between the ribs (45° from a rib), causingmaximum side loading deflection. Additionally, the solid design of thestopper rod adds unnecessary material costs to the rod and mayundesirably flex in an axial direction during use.

SUMMARY OF THE INVENTION

There is a need in the art for a stopper design that is self-centeringto insure a seal with the syringe outlet to allow for pressuregeneration to create a positive displacement. There is a further need inthe art for a stopper design that creates an active seal via theinteraction of the stopper and plunger rod to transmit a radial forcewith respect to the barrel. The concept of an active seal is that anincrease in pressure inside the syringe barrel that will cause theforward seal of the stopper to have a higher contact pressure with theinside walls of the barrel to always maintain a higher contact pressurethan the internal fluid pressure thereby preventing leakage at thestopper seal. There is yet another need in the art for a stopper designthat includes a feature, which allows for the capture and storage ofpotential energy prior to the release of the force from the plunger rodeffectively and consistently reducing and/or eliminating reflux of fluidback into the syringe upon this release of pressure on the plunger rod.There is also a need in the art for a plunger rod attachment designwhich can be easily inserted into the stopper of a pre-filled,sterilized syringe with the application of minimal force thereto andwhich is securely held within the stopper during use of the syringe.There is a further need in the art for a plunger rod design that uses areduced amount of processing material, has a reduced molding cycle time,and has a high resistance to side loading.

According to one aspect of the invention, a plunger rod adapted forattachment is disclosed with a stopper for use with a syringe barrel.The plunger rod includes an elongated member having a front end and aback end, which extends along a longitudinal axis. The plunger rodfurther includes at least one deflecting arm associated with the frontend of the elongated member. The deflecting arm is capable of deflectingradially inward during insertion of the plunger rod into a stopper anddeflecting outward into contact with an inner surface of the stopperafter insertion into such stopper to lock the plunger rod within thestopper. The plunger rod can include at least two deflecting arms. Theplunger rod can also include at least a first stop member for limitingdeflection of the deflecting arm during insertion of the plunger rodinto the stopper. The front end of the elongated member comprises a headmember extending from the front end and including a rim member extendingalong a front surface thereof. According to one design, the at least onedeflecting arm extends rearward from a bottom surface of the rim memberand the first stop member is positioned adjacent to a rearward portionof the head member. According to another design, the at least onedeflecting arm extends from a center portion of the head member and thefirst stop member extends outward from a rearward portion of the headmember. A second stop member extends rearward from a bottom surface ofthe rim member to limit arm deflection of the deflecting arm. Accordingto yet another design, the at least one deflecting arm extendsrearwardly from a bottom surface of the rim member and the first stopmember extends outward from a rearward portion of the head member. Inthis design, a second stop member can be provided for extending downwardfrom an outer edge of the rim member to limit arm deflection of thedeflecting arm. According to still another design, the front end of theelongated member includes a base member having a head member extendingfrom a front end. The head member includes a rim member extending alonga front surface thereof and wherein the at least one deflecting armcomprises a first arm portion extending from the base member parallelwith the head member and a second arm portion attached to a frontportion of the first arm portion extending in a rearward and outwarddirection with respect to the first arm portion. This design furtherincludes a stop member to limit deflection of the second arm portionduring insertion of the plunger rod into the stopper. The stop member ispositioned adjacent an outer surface of the first arm portion at alocation adjacent to an inner surface of the second arm portion.

According to another aspect of the invention, the front end of theelongated member of the plunger rod includes a head member having a rimmember extending along a front surface thereof and wherein the rimmember is formed from a material capable of forming an active seal withan inside surface of the stopper. The head member and the rim memberinclude a hollow portion defined by at least one sidewall wherein thesidewall has a plurality of inwardly extending ribs extending toward thecenter of the hollow portion for contacting the inside surface of thestopper. The rim member includes a taper adapted for contacting acorresponding taper within the stopper for applying a radial force tothe stopper upon the application of a forward force to the plunger rod.According to one design, the deflecting arm includes either at least twodeflecting arms or a single circular deflecting arm extending from thefront end of the elongated member so as to define a space wherein uponinsertion of the plunger rod into the stopper, a slug is inserted intothe space to prevent one or all of the deflecting arm from collapsingduring aspiration of the syringe. According to another design, theelongated member can be hollow and the slug is pre-molded within theelongated member and an application force is applied within the hollowmember to force the slug into the space. The deflecting arm can includea taper at a forward end thereof adapted for contacting a correspondingtaper within the stopper for applying a radial force to the stopper uponthe application of a forward force to the plunger rod.

According to another aspect of the invention, there is disclosed aplunger rod adapted for attachment with a stopper for use with a syringebarrel. The plunger rod includes an elongated hollow member having afront end, a back end, and a sidewall portion extending along alongitudinal axis between the front end and the back end. The sidewallportion comprises a plurality of longitudinally extending lobes definingan interior hollow portion. An attachment member is secured to the frontend adapted for attachment of the plunger rod to the stopper and a covermember is secured to the back end of the elongated member for coveringthe hollow portion and providing a thumb press area for application of aforce to the plunger rod during use. According to one design, thelongitudinally extending lobes can include an odd number of lobes spacedsubstantially equidistant with respect to one another, for example, atapproximately 120° with respect to one another for a three lobe design.The lobes are positioned with respect to one another to formsubstantially uniform side loading deflection of the plunger rod. Theelongated member and the front end attachment member can be integrallymolded from the same material. Alternatively, each of the elongatedmember, the front end attachment member, and the back end cover membercan be formed separately from different materials.

According to yet another aspect of the invention, there is disclosed aplunger rod and stopper assembly adapted for use with a syringe barrel.The assembly includes a plunger rod having a front attachment end and aback end extending along a longitudinal axis. The assembly furtherincludes at least one deflecting arm associated with the attachment endof the elongated member. The deflecting arm is adapted to deflectradially inward upon an application of force thereto and to deflectradially outward upon a release of such force. The assembly additionallyincludes a stopper having a main body defining an open rearward end anda closed front end. The open rearward end is defined by an inside wallsurface and an undercut portion. The open end is adapted for receivingthe front attachment end of the plunger rod such that the deflecting armis deflected during insertion of the front attachment end and deflectsoutward after insertion to become trapped between at least a portion ofthe inside wall surface and the undercut portion to lock the plunger rodwithin the stopper. The front attachment end of the plunger rod includesa head member extending from the front end. The head member includes arim member extending along a front surface thereof and includes a taperadapted for contacting a corresponding taper within the stopper forapplying a radial force to the stopper upon the application of a forwardforce to the plunger rod. According to one embodiment, the correspondingtaper of the stopper can include a continually tapering surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a plunger rod, stopper, andsyringe barrel in accordance with an embodiment of the presentinvention.

FIG. 2A is a perspective view of a stopper according to a firstembodiment of the present invention.

FIG. 2B is a cross-sectional side view of the stopper of FIG. 2A takealong line 2B-2B.

FIG. 3 is a cross-sectional side view of the stopper of FIG. 2A attachedto a plunger rod and positioned within a syringe barrel.

FIG. 4A is a perspective view of a stopper according to a secondembodiment of the invention in accordance with an embodiment of thepresent invention.

FIG. 4B is a cross-sectional side view of the stopper of FIG. 4A takenalong line 4B-4B.

FIG. 5A is a side view of the stopper according to a third embodiment ofthe invention in accordance with an embodiment of the present invention.

FIG. 5B is a cross-sectional view of the stopper taken along line 5B-5Bof FIG. 5A.

FIG. 6A is a perspective view of a stopper according to a fourthembodiment of the invention in accordance with an embodiment of thepresent invention.

FIG. 6B is a cross-sectional side view of a stopper having an exteriordesign of FIG. 6A taken along line VI-VI of FIG. 6A and having aninterior design according to the first embodiment of the invention shownin FIG. 2B.

FIG. 6C is a cross-sectional side view of a stopper having an exteriordesign of FIG. 6A taken along line VI-VI of FIG. 6A and having aninterior design according to the second embodiment of the inventionshown in FIG. 4B in combination with one type of an attachment portionof a syringe plunger rod.

FIG. 6D is a cross-sectional side view of a stopper having an exteriordesign of FIG. 6A taken along line VI-VI of FIG. 6A and having aninterior design as shown in FIG. 6C in combination with an alternativetype of attachment portion of a syringe plunger rod.

FIG. 6E is a cross-sectional side view of a stopper assembly having amodified skirt in accordance with an embodiment of the presentinvention.

FIG. 6F is a cross-sectional side view of a stopper assembly in whichthe skirt has been eliminated in accordance with an embodiment of thepresent invention.

FIG. 7 is a cross-sectional side view of the stopper of FIG. 6Bpositioned within a syringe barrel.

FIG. 8 is a cross-sectional side view of the stopper of FIG. 6Cpositioned within a syringe barrel.

FIG. 9 is a cross-sectional side view of the stopper of FIG. 6Dpositioned within a syringe barrel.

FIG. 10 is a cross-sectional side view of a stopper/plunger arrangementutilizing the stopper of FIG. 2B during a first reflux reduction step ofthe invention.

FIG. 11 is a cross-sectional side view of a stopper/plunger arrangementutilizing the stopper of FIG. 2B during a second reflux reduction stepof the invention.

FIG. 12 is a cross-sectional side view of a stopper/plunger arrangementutilizing the stopper of FIG. 2B during a third reflux reduction step ofthe invention.

FIG. 13 is a cross-sectional side view of a stopper/plunger arrangementutilizing the stopper embodiment of FIG. 6C during a first refluxreduction step of the invention.

FIG. 14 is a cross-sectional side view of a stopper/plunger arrangementutilizing the stopper embodiment of FIG. 6C during a second refluxreduction step of the invention.

FIG. 15 is a cross-sectional side view of a stopper/plunger arrangementutilizing the stopper embodiment of FIG. 6C during a third refluxreduction step of the invention.

FIG. 16A is a perspective view of the plunger rod of FIG. 1.

FIG. 16B is a side view of the plunger rod of FIG. 1.

FIG. 16C is a top view of the plunger rod of FIG. 1.

FIG. 17A is an enlarged perspective view of the attachment member forthe plunger rod of FIG. 1 according to a first embodiment of theinvention.

FIG. 17B is a side view of the attachment member of FIG. 17A.

FIG. 18A is an enlarged perspective view of the attachment member forthe plunger rod according to a second embodiment of the invention.

FIG. 18B is a side view of the attachment member of FIG. 4A.

FIG. 19A is an enlarged perspective view of the attachment member forthe plunger rod according to a third embodiment of the invention.

FIG. 19B is a side view of the attachment member of FIG. 19A.

FIG. 20A is an enlarged perspective view of the attachment member forthe plunger rod according to a fourth embodiment of the invention.

FIG. 20B is a side view of the attachment member of FIG. 6A.

FIG. 20C is a side view of the attachment member of FIG. 6A includingstop members.

FIG. 21A is a perspective view of the plunger rod including anattachment member according to a fifth embodiment of the invention.

FIG. 21B is a perspective view of the plunger rod of FIG. 21A includinga reinforcing slug located within the attachment member.

FIG. 21C is a side view of the plunger rod of FIG. 21B.

FIG. 21D is a side view of the plunger rod of FIG. 21A wherein thereinforcing slug is positioned within a hollow portion of the plungerrod.

FIG. 21E is a cross-sectional side view taken along line 21E-21E of FIG.21C.

FIG. 21F is a top view of the attachment member of FIG. 21B.

FIG. 22A is an exploded perspective view of the plunger rod according toone embodiment of the invention.

FIG. 22B is a cross-sectional view of the plunger rod of FIG. 21A takenalong line 22B-22B.

FIG. 23A is a side view of the plunger rod according to a secondembodiment of the invention.

FIG. 23B is a cross-sectional view of the plunger rod of FIG. 23A takenalong line 23B-23B.

FIG. 24A is a side view of the plunger rod according to a thirdembodiment of the invention.

FIG. 24B is a cross-sectional view of the plunger rod of FIG. 24A takenalong line 24B-24B.

FIG. 25 is an exploded side view of the individual components of theplunger rod, which may be separately formed, in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”,“longitudinal” and derivatives thereof shall relate to the invention asit is oriented in the drawing figures. However, it is to be understoodthat the invention may assume various alternative variations, exceptwhere expressly specified to the contrary. It is also to be understoodthat the specific devices illustrated in the attached drawings, anddescribed in the following specification, are simply exemplaryembodiments of the invention. Hence, specific dimensions and otherphysical characteristics related to the embodiments disclosed herein arenot to be considered as limiting.

Reference is now made to FIG. 1, which shows a perspective view of asyringe, generally indicated as 10. The syringe comprises a stopper 12and a plunger rod 14. The stopper 12 and plunger rod 14 are adapted foruse within a syringe barrel 16. The syringe 10 is preferably of a typethat is pre-filled and sterilized for use in flush applications. Thesyringe barrel 16 includes a distal or frontal end 18 which includes anoutlet opening and/or a mechanism for attachment of a separate medicaldevice (such as a catheter), shown in the form of a luer 20, and an openproximal or rearward end 22 for receiving the stopper 12 and plunger rod14 assembly. While the figures herein depict a separate stopper andplunger assembly, it is contemplated that the stopper features may beintegrally formed with a plunger rod 14.

Reference is now made to FIGS. 2A, 4A, and 6A which show perspectiveviews of the positive displacement stopper 12 according to severaldifferent embodiments of the invention. FIGS. 2B, 4B, and 6B-6D showcross-sectional views of the different stopper embodiments in which thedetails of the positive displacement features of the stopper withrespect to the syringe 10 can be readily viewed, wherein like elementsare denoted by consistent numbering between the figures. The stopper 12is adapted for attachment with a plunger rod 14 for use within a syringebarrel 16. The stopper 12 is preferably made of an elastomeric materialselected from the group of natural rubber, synthetic rubber,thermoplastic elastomers, or combinations thereof. The stopper 12 of theinvention is particularly useful with flush syringes such as those foruse in connection with a catheter, as is well known in the art.

The stopper includes a main body 26 defining an open rearward end 28 anda closed front end 30. The open rearward end 28 is adapted to receivethe front forward end attachment portion 31 of the plunger rod 14. Thefront forward end attachment portion 31 can be of any known design whichis capable of attachment to the stopper 12; however, the presentinvention includes several inventive attachment members which areadapted for use with the stopper 12 of the present invention. Theseinventive attachment members are discussed in further detail below.

The stopper 12 further includes a flexible core member 32 integrallyformed with the main body 26 adjacent the closed front end 30. As shownin FIG. 3, the flexible core member 32 includes a nose portion 34 havinga profile adapted to be self-centering such that even when the stopper12 is not centered in the syringe barrel 16, it creates a positive sealwith an outlet opening of the syringe barrel 16, such as an interiorsurface 36 of a luer 20 of the syringe barrel 16. Once the stopper 12has traveled the full distance through the syringe barrel 16 andcontacts the internal surface at the forward wall or interior surface 36of the syringe barrel 16 a positive seal may be formed therewith. In oneembodiment, the nose portion 34 has a semi-spherical shape, which isself-centering such that even when the stopper 12 is not centered in thesyringe barrel 16, it creates a positive seal with the outlet opening orluer 20 once the stopper 12 is bottomed in the syringe barrel 16. Thenose portion 34 of the flexible core member 32 may include other shapessuch as substantially conical, cubic, and/or any other volumetric shapecapable of self-centering itself with respect to an outlet opening orluer 20 of the syringe barrel 16. This seal prevents excess fluid frombeing forced out of the syringe 10 once the stopper 12 is bottomed inthe syringe barrel 16. Excess fluid expelled at the end of an injectioncan cause a phenomenon known as “reflux” when the stopper 12 springsback to shape and pulls that excess fluid back into the syringe 10. Inthe design of the present invention, the seal also allows the buildup ofpressure within the fluid trapped between the stopper 12 and the syringebarrel 16, which in turn will lead to positive displacement of the fluidonce pressure is released. This positive displacement of the fluid toprevent reflux is discussed in more detail below.

The flexible core member 32 includes a front portion 38, a back portion46, and a central portion 42, positioned between the front portion 38and back portion 40. The front portion 38 projects from the main body26, such as along a longitudinal axis of the main body 26. The flexiblecore member 32 may be interconnected with the main body 26 via aflexible membrane 44 extending between the flexible core member 32 andthe main body 26. The back portion 40 of this flexible core member 32contacts the front forward end attachment portion 31 of the plunger rod14. The inventive design of the self-centering nose portion 34 allowsfor a seal to be made when a small amount of force is applied to thestopper 12 and over the entire tolerance ranges of the stopper 12 andsyringe barrel 16.

As discussed above, the sealing surface on the nose portion 34 comesinto contact with the interior surface 36 or back surface of the conicalluer 20 at the front end of the syringe barrel 16, shown in FIG. 1.Since it is possible that the interior surface 36 of the luer 20 and thenose portion 34 of the stopper 12 will not be perfectly concentric, inone embodiment, the nose portion 34 of the stopper 12 may be capable ofmoving laterally in order for it to make full contact with the interiorsurface 36 of the luer 20. In a further embodiment, the flexible coremember 32 and the flexible membrane 44 may allow the nose portion 34 tomove in a substantially lateral direction. In yet another embodiment,the partially spherical shape of the nose portion 34 assures fullcontact between the nose portion 34 and the interior surface 36 of theluer 20 even when the nose portion 34 has rotated or shifted prior tomaking contact.

The inventive design of the stopper 12 of the present invention is animprovement over current stoppers as these current stoppers typicallyhave a conical tip and work to seal only when the stopper and barrel areperfectly concentric. In prior designs, if the two components are notexactly aligned, there will not be a proper seal unless higher forcesare applied to the stopper in order to deform it into a shape that willseal with the barrel luer taper.

According to a first embodiment of the stopper 12, as illustrated inFIGS. 2A, 2B, and 3, and a second embodiment of the stopper 12, asillustrated in FIGS. 4A and 4B, the main body 26 includes at least afirst rib 46 extending radially outward and substantially around aperimeter of the main body 26. This first rib 46 is adapted for formingan active seal with the syringe barrel 16. In one embodiment, the mainbody 26 includes a second rib 48 extending substantially around aperimeter of the main body 26. The first rib 46 and the second rib 48may be axially spaced apart along the length of the main body 26.

A feature of the stopper design of the first embodiment illustrated inFIGS. 2A, 2B and 3 is a forward extending skirt 50 extending from theclosed front end 30 of the main body 26. Due to the elasticity and/orflexibility of the forward extending skirt 50, the forward extendingskirt 50 is capable of deforming by deflecting radially inwardly towardand substantially in contact with an outer portion 52 of the main body26. Such deflection may occur upon insertion of the stopper 12 withinthe syringe barrel 16 to form an air pocket 53 to trap an air bubbletherein. The air bubble trapped within air pocket 53 assists in theanti-reflux capabilities of the present invention as discussed in detailbelow. Upon insertion of the stopper 12 into the syringe barrel 16, theforward extending skirt 50 may be adapted to create a positive pressurewithin the syringe barrel 16.

In one embodiment, the main body 26 includes at least one undercutportion 55 extending axially inward from the open rearward end 28. Theundercut portion 55 is adapted to engage the front forward endattachment portion 31 of the plunger rod 14 for locking the frontforward end attachment portion 31 of the plunger rod 14 within thestopper 12. According to one embodiment, as shown in FIG. 3, theundercut portion 55 can include a reverse taper 56 adapted forcooperation with at least one deflecting arm 130 associated with thefront forward end attachment portion 31 of the plunger rod 14.

The stopper 12 of the present invention may also be adapted to reduceand/or prevent mid-stream reflux. Mid-stream reflux occurs if the flushsolution is not fully infused and the clinician does not clamp the linewhile the stopper is moving. Traditional syringe designs will generatereflux as the friction force on the stopper outer diameter and theplunger rod forces on the stopper center “stretch” the stopper nose. Inorder to overcome the static and dynamic friction to cause the stoppermovement, the plunger rod force must be larger than the friction force,and this force imbalance is offset by the fluid back pressure and thestopper stretching. The difference is small, but measurable. As shown inFIG. 3 of the present application, a gap 94 is provided between a backportion 93 of the flexible core member 32 of the stopper 12 and the face95 of the front forward end attachment portion 31 of the plunger rod 14.Because of this gap 94 and the flexibility of the flexible membrane 44attaching the flexible core member 32 to the stopper main body 26, theflexible core member 32 is able to deflect proximally and storepotential energy that is released in the form of positive displacementas soon as the plunger rod 14 force is ceased. Accordingly, during useof the syringe 10, due to gap 94, the plunger rod 14 does not directlyapply a forward force to the flexible core member 32. Instead theplunger rod 14 applies a forward force to the interior side portion ofthe stopper 12 which, in turn, applies a pulling force to the flexiblecore member 32 via flexible membrane 44. Thus, during the application ofpressure to the plunger rod, the flexible core member 32 is slightlyretracted into the gap 94. Once the forward force is suspended, theflexible core member 32 continues this forward motion and preventsmid-stream reflux.

According to one aspect of the invention, as depicted in FIGS. 2B, 3,and 4B, the interior portion of the main body 26 includes an innersurface 132 having a taper 198 adapted for contact with a taper 196 onthe front forward end attachment portion 31 of the plunger rod 14. Thesecontacting tapers 196, 198 cooperate together such that the stopper 12applies a radial force to the syringe barrel 16 to form an active sealtherewith upon the application of a forward force to the plunger rod 14.The active seal aspect of the invention is discussed in detail below.

In accordance with a second embodiment of the invention, as illustratedin FIGS. 4A and 4B, the flexible membrane 44A may extend from theflexible core member 32 to the sidewall portion 57A of the main body 26terminating at the first rib 46A. In one arrangement, the flexiblemembrane 44A, first rib 46A and sidewall 57A are integrally formed. In afurther configuration, the forward extending skirt 50 of the firstembodiment is not included.

According to a third embodiment of the invention, as illustrated inFIGS. 5A and 5B, an active seal achieves the same result as that of thepreviously discussed embodiments, but with a different mechanism,commonly referred to as a “Lip Seal” when used in hydraulicapplications. The stopper, generally indicated as 254, includes this lipseal. The front seal 256 of the stopper 254 is located on the leadingedge of a flexible arm 258. Initial sealing pressure is generated by theinterference of the flexible arm 258 with the wall of the syringe barrel16, as shown in FIG. 1. When the pressure in the syringe barrel 16increases, this pressure applies an outward radial force to the inside259 of the flexible arm 258. This outward force will increase the forcewith which the seal 256 presses against the inside wall of the syringebarrel 16.

Reference is now made to FIGS. 6A-6F and 7-9 which show the stopper 12according to a fourth embodiment of the invention. In this embodiment,the stopper 12 includes a main body 26 having a closed front end 30. Themain body 26 can include an open rearward end 28 which is adapted toreceive a front forward end attachment portion 31 of the plunger rod 14.As stated above, the front forward end attachment portion 31 is capableof attachment to the stopper 12. The main body 26 includes a first bodyportion 60 having a first diameter D1, as shown in FIG. 6B, and a secondbody portion 62 having a second diameter D2, as shown in FIG. 6B, whichis larger than the first diameter of the first body portion 60. Ashoulder 64 extends around a perimeter of the first body portion 60 ofthe main body 26. Preferably, this shoulder 64 extends in a radiallyoutward direction with respect to the first body portion 60.

As stated above with respect to the description of the first embodiment,a flexible core member 32 is integrally formed with the main body 26adjacent the closed front end 30. The flexible core member 32 includes anose portion 34 extending from the closed front end 30 which is adaptedfor contacting an interior surface 36 of an outlet opening, such as aluer 20 of the syringe barrel 16. The flexible core member 32 may beformed from a flexible material and the nose portion 34 may include asemi-spherical self-centering profile to create a positive seal with theluer 20 at the forward end of the syringe barrel 16.

The stopper 12 of the fourth embodiment, shown in FIGS. 6A-6E, differsfrom the first embodiment in that the stopper 12 includes at least oneperimetrical skirt 66 extending from the second body portion 62 towardthe front end 30 of the main body 26. This perimetrical skirt 66cooperates with the shoulder 64 for trapping air pockets or an airbubble 68 therebetween upon insertion and/or movement of the stopper 12within and through the syringe barrel 16. In this manner, upon releaseof a forward force on the plunger rod 14, fluid remaining within thesyringe barrel 16 is forced through the luer 20 through positivedisplacement thereof. As shown in detail in FIGS. 6B-6D, the skirt 66may include an inner surface 70 and an outer surface 72 and may beformed from a flexible and/or elastic material capable of deflectingradially inwardly. The inner surface 70 of the perimetrical skirt 66 maysubstantially contact the shoulder 64 to trap at least one airpocket/bubble 68. In one embodiment, the skirt 66 includes a lip portion74 and a tail portion 76. The lip portion 74 may include an outwardlyextending bump or first rib 77. An outer surface 77′ of the first rib 77may be adapted for contact with an inner surface 78 of the wall of thesyringe barrel 16, shown in FIG. 1. This first rib 77 establishes asingle line of contact between the perimetrical skirt 66 and the innersurface 78 of the wall of the syringe barrel 16, as shown in FIGS. 7-9.This first rib 77 functions to keep an outer surface 69 of theperimetrical skirt 66 adjacent the tail portion 76, positioned apredetermined distance apart from the inner surface 78 of the wall ofthe syringe barrel 16. This minimizes the area of contact between theperimetrical skirt 66 and the syringe barrel 16 to reduce break-looseforces and reduce static friction of the perimetrical skirt 66 withrespect to the syringe barrel 16. The particular design of theperimetrical skirt 66 may allow for a clearer observation of the dosesetting. In one embodiment, the perimetrical skirt 66 has a relativelylinear shape and extends in a cylindrical manner about the first bodyportion 60 of the main body 26. According to another embodiment, theinner surface 70 of the perimetrical skirt 66 does not necessarilycontact the main body 26 to form the air pocket or chamber 68, but isclose enough to the main body 26 such that surface tension keeps thechamber 68 closed off and traps an air bubble therein.

As shown in FIGS. 6B-6D, the perimetrical skirt 66 of the stopper 12 isdimensioned to have a predetermined contact area 80 for cooperation withthe shoulder 64. The contact area 80 is adapted for forming apredetermined gap sufficient for trapping air and allowing forcommunication of pressure from an air chamber to a fluid chamber.

FIG. 6E shows a modification of the stopper 12 of the fourth embodimentwherein the skirt 366 has a predetermined length L1 which is less thanthe length L2 of the perimetrical skirt 66 of FIGS. 6B-6D and less thanthe height H1 of the shoulder 364 such that the predetermined contactarea 380 contacts a bottom surface 365 of the shoulder 364 to form theair pressure chamber 368.

According to another arrangement, as shown in FIG. 6F, an air pressurechamber 468 can be created solely by the cooperation of the radiallyextending shoulder 464 with the inner surface 478 of the syringe barrel416. In this configuration, the tip 467 of the shoulder 464 does nothave to actually contact the inner surface 478 of the wall of thesyringe barrel 16 in order to create the air pressure chamber 468, butrather only needs to be within a certain distance with respect to thisinner surface to close off the air pressure chamber 468.

Referring again to FIGS. 6A-6F, the flexible core member 32 of thestopper 12 of the invention includes a front portion 82, extending abovethe main body 26, a back portion 84 and a central portion 86 positionedbetween the front portion 82 and back portion 84. The flexible coremember 32 is interconnected with the main body 26 and, in particular,with the first body portion 60 thereof via a flexible membrane 44extending between the central portion 86 of the flexible core member 32and the first body portion 60 of the main body 26. The inventive designof the self-centering nose portion 34 allows for a seal to be madebetween the nose portion 34 and the interior surface 36 of an outletopening or luer 20 when a small amount of force is applied to thestopper 12 and over the entire tolerance ranges of the stopper 12through the plunger rod 14 and syringe barrel 16. As discussed above inrelation to the first embodiment, the partially spherical surface shapeof the nose portion 34 of the flexible core member 32 ensures fullcontact between the nose portion 34 and the interior surface 36 of theluer 20, even when the nose portion 34 has rotated or shifted prior tomaking contact.

The flexible membrane 44 and the air pocket/bubble 68 are adapted forstoring potential energy such that upon release of a positive pressureon the plunger rod 14 and release of the seal between the nose portion34 of the flexible core member 32 and the interior surface 36 of theluer 20, release of this potential energy forces fluid within thesyringe barrel 16 through the luer 20 and any attached catheter.

According to the fourth embodiment of this invention, the main body 26includes at least a second rib 88 extending substantially radiallyoutward and substantially around a perimeter of the second body portion62 of the main body 26. This second rib 88 is adapted to form an activeseal with the inner surface 78 of the syringe barrel 16. The at leastone air pocket/bubble 68 is positioned in a forward position withrespect to the second rib 88. The main body 26 may include a third rib90 such that the second rib 88 and third rib 90 extend radially outwardaround the perimeter of the outer diameter D2, as shown in FIG. 6B, ofthe second body portion 62 of the main body 26 and are axially spacedapart along this second body portion 62.

As shown in FIGS. 6B-6F and FIGS. 7-9, the main body 26 of the stopper12 can include at least one undercut portion 55 extending axially inwardof the open rearward end 28. This undercut portion 55 is adapted forlocking the front forward end attachment portion 31 of the plunger rod14 within the stopper 12. According to one aspect, the undercut portion55 may include a reverse taper 56, as shown, for example in FIG. 7,which is adapted for cooperation with the front forward end attachmentportion 31 of the plunger rod 14. Various designs of the front forwardend attachment portion 31, according to the present invention arediscussed in detail below.

As shown in FIG. 6B and FIG. 7, the main body 26 may also include aninner surface having a taper 198 adapted for contact with a taper 196 onthe front forward end attachment portion 31 of the plunger rod 14. Thesecontacting tapers 196, 198 cooperate together such that the stopper 12applies a radial force to the syringe barrel 16 to form an active sealtherewith upon the application of a forward force to the plunger rod 14.

According to another aspect of the invention, as depicted in FIGS. 6C,6D, 8, and 9, the taper 199 of the inner surface 132 of the main body 26may be a continuous contour from a sidewall portion 57 of the main body26 to the flexible core member 32. This continuous contour taper 199 isadapted for cooperating with taper 196 on the front forward endattachment portion 31 of the plunger rod 14 such that the stopper 12applies a radial force to the syringe barrel 16 to form an active sealtherewith upon the application of a forward force to the plunger rod 14.

An increase in pressure inside the syringe barrel 16 will cause theclosed front end 30 of the stopper 12 to have a higher contact pressurewith the inner surface 78 of the wall of the syringe barrel 16, therebypreventing leaks at the stopper 12 and syringe barrel 16 seal. Theactive seal of the present invention solves this problem by using alower contact pressure between the stopper 12 and syringe barrel 16 whenthere are low fluid pressures in the syringe barrel 16, but highercontact pressure when the fluid pressure increases, such as duringforward movement of the plunger rod 14 and stopper 12 through thesyringe barrel 16.

In one embodiment, the active seal is achieved through the interactionof the front forward end attachment portion 31 of the plunger rod 14 andthe inside of the stopper 12. According to one embodiment, as shown inFIG. 6B, the front forward end attachment portion 31 of the plunger rod14 includes a forward leading surface taper 196 and corresponds to ataper 198 on the inside of the stopper 12. During use when the plungerrod 14 is being pushed, a forward leading edge applies force to theinside of the stopper 12. Due to the shape of the taper of the twosurfaces 196, 198, the plunger rod 14 imparts a force that pushes thestopper 12 forward in the syringe barrel 16 and a force that pushessubstantially outward in a radial direction. The outward force advancesthe stopper 12 forward of the second rib 88, and into the walls of thesyringe barrel 16 which increases the sealing pressure. Likewise, asshown in FIGS. 6C and 6D, the taper 196 on the front forward endattachment portion 31 of the plunger rod 14 imparts a force to thecontinuous contour taper 199 of the inner surface 132 of the main body26 such that the stopper 12 applies a radial force to the syringe barrel16 to form an active seal therewith upon the application of a forwardforce to the plunger rod 14. High plunger rod forces are caused by highpressure in the syringe barrel 16, such that contact pressure therewithwill increase as pressure in the syringe barrel 16 increases.

In a further embodiment, the perimetrical skirt 66 of the stopper 12also acts as a lip seal. As the fluid pressure increases, increasing theair pressure in the air pocket/bubble 68, the skirt contact pressure atthe interface of stopper 12 and syringe barrel 16 is increased,improving the sealing performance. Another advantage of this active sealis due to the application of the force of the plunger rod 14 only on theforward or second rib 88, which allows the back or third rib 90 to be“pulled” forward during injections. The pulling will also stretch thematerial of the back or third rib 90 reducing the effective force on thesyringe barrel 16 and further reducing friction forces.

The stopper design of the present invention is intended to preventreflux by creating positive displacement of fluid out of the front endof the syringe barrel (and into any attached catheter) after the stopper12 has been bottomed in the syringe barrel 16 and force is released fromthe plunger rod 14. The features of the stopper 12 that act to createthis positive displacement are the seal at the nose portion 34 of thestopper 12, the flex or relative movement of the stopper 12 between thenose portion 34 and the forward or second sealing rib 88, and potentialenergy in the form of pressurized fluid captured and stored prior to therelease of the force from the plunger rod 14. The relative movement ofthe second rib 88, with respect to the nose portion 34 of the stopper12, is achieved by means of the flexible membrane 44 that connects theouter forward or second rib 88, to the flexible core member 32 and noseportion 34. The energy storing is achieved by means of both the flexiblemembrane 44 and an air bubble or air pocket 68 that is trapped under theperimetrical skirt 66 just forward of the second rib 88.

The particular design of the fourth embodiment of the stopper 12 of thepresent invention has several advantages. For example, since theperimetrical skirt 66 may be substantially linear, without any radialflanges, wrinkling of the perimetrical skirt 66 is reduced and/oreliminated. In particular, the provision of the shoulder 64 on the firstbody portion 60 of the stopper main body 26 allows the perimetricalskirt 66 to have a relatively straight shape and the flexibility and/orelasticity of the perimetrical skirt 66 allows for flex in an inwarddirection to bring a contact area 80 of the perimetrical skirt 66,without deformation of the perimetrical skirt 66 itself, into contactwith the shoulder 64. Another advantage of this design is thatmanufacturing of the stopper 12 is simplified. As only one molding toolplate is required for the bottom of the mold, the cost of the tooling isreduced.

The addition of the outwardly extending portion or bump 77 on theperimetrical skirt 66 minimizes the area of the perimetrical skirt 66 incontact with the inner surface 78 of the syringe barrel 16. This reducedcontact area reduces break-loose forces and static friction and alsoprovides a clear indication of the does setting. Finally, the design ofthe interference and length of the perimetrical skirt 66 is such tomaintain the proper gap to trap air and allow, for communication ofpressure from the air chamber to the fluid chamber.

An active seal of the stopper 12 within the syringe barrel 16 can befurther achieved by the front forward end attachment portion 31 of theplunger rod 14, as described below, in combination with the particularinterior design of the stopper 12. The front forward end attachmentportion 31 is adapted for use with any of the stopper embodimentspreviously disclosed herein. The invention is particularly useful insituations wherein the syringe 10 is pre-filled and sterilized and thestopper 12 is inserted into the syringe barrel 16 prior to attachment ofthe plunger rod 14 to the stopper 12.

As illustrated in FIGS. 16A-16C, the plunger rod 14 may include anelongated member 124 having a front end 126 and a back end 128 extendingalong a longitudinal axis AX, as shown in FIG. 16B. At least onedeflecting arm 130 may be associated with the front end 126 of theelongated member 124. The deflecting arm 130 may be capable ofdeflecting radially inward during insertion of the plunger rod 14 intothe stopper 12, and deflecting outward into contact with an innersurface 132 of the stopper 12, as shown in FIG. 3, after insertion intothe stopper 12 to lock the plunger rod 14 within the stopper 12. FIGS.16A-16C illustrate two deflecting arms 130, however, any number ofdeflecting arms 130 can be provided as needed to securely attach theplunger rod 14 within the stopper 12.

Referring back to FIG. 3, when the plunger rod 14 is inserted into thestopper 12, the deflecting arms 130 on the plunger rod 14 deflect and/orthe stopper 12 deforms to allow the deflecting arms 130 to move into anundercut space 134 on the inside of the stopper 12. When the deflectingarms 130 enter the undercut space 134, the plunger rod 14 is locked inplace and is prevented from separating from the stopper 12. When a useruses the syringe 10 to aspirate, the deflecting arms 130 on the plungerrod 14 will dig into the undercut surface 136 of the stopper 12, on theinside of the stopper 12, preventing the plunger rod 14 from pulling outof the stopper 12. The bottom surface 133 of the deflecting arm 130 canbe tapered to correspond with the shape of the undercut surface 136 ofthe stopper 12. The deflecting arms 130 can be implemented according toseveral designs, as discussed in detail below.

According to a first embodiment, as illustrated in FIGS. 17A-17B, thefront end 126 of the elongated member 124 includes a head member 140extending from a front surface 144 of the front end 126. The head member140 includes a rim member 142 extending along a front surface 144thereof. The deflecting arms 130 may extend from a bottom surface 146 ofthe rim member 142 in a substantially downward direction. At least afirst stop member 148 may be provided for limiting deflection of thedeflecting arms 130 during insertion of the plunger rod 14 into thestopper 12. This first stop member 148 can be positioned adjacent to arearward portion 150 of the head member 140.

The rim member 142 is preferably formed from an elastomeric materialcapable of forming an active seal with an inside surface of the stopper12, as shown in FIG. 3. A reinforcement material 153 may also beprovided at the contact area of the deflecting arms 130. Also, as shownin FIGS. 16A, 16C, and 17A, the rim member 142 and head member 140 mayinclude a hollow portion 156 defined by at least one sidewall 158. Thesidewall 158 has a plurality of inwardly extending ribs 159 extendingradially inward toward the center of the hollow portion 156. Accordingto one embodiment, this hollow portion 156 can come into contact with aback portion of the flexible core member 32 inside of the stopper 12.

According to a second embodiment, as illustrated in FIGS. 18A-18B, theat least one deflecting arm 160 extends radially outwardly from a centerportion 162 of the head member 140. In this embodiment, the deflectingarm 160 may be a continuous member that extends through an aperture 163in the center portion 162 of the head member 140. A hollow portion 166is also provided in the head member 140 and rim member 142 of thisembodiment. The edges 168 of the deflecting arm 160 may also be formedfrom appropriate reinforcement material. A first stop member 170 extendsoutward from a rearward portion 150 of the head member 140. A secondstop member 172 extends rearward from a bottom surface 173 of the rimmember 142 to limit arm deflection in an opposite direction, such asduring aspiration of the syringe 10.

According to a third embodiment, as illustrated in FIGS. 19A-19B, the atleast one deflecting arm includes a pair of deflecting arms 174extending in a downward and radially outward direction from the bottomsurface 173 of the rim member 142. In this embodiment, a first stopmember 176 extends outward from a rearward portion 150 of the headmember 140. A second stop member 178 extends downward from an outer edge179 of the rim member 142 for limiting deflection of the deflecting arms174, such as during aspiration. The edges 180 of deflecting arms 174 areformed from appropriate reinforcement material.

According to a fourth embodiment, as illustrated in FIGS. 20A-20C, thefront end 126 of the elongated member 124 includes a base surface 126Ahaving a head member 140 extending therefrom. The head member 140includes a rim member 142 extending along a front surface 144 thereof.In this embodiment, the at least one deflecting arm includes a first armportion 182 extending from the base surface 126A parallel with the headmember 140 and a second arm portion 184 attached to a front portion 186of the first arm portion 182 extending in a rearward and outwarddirection with respect to the first arm portion 182. A stop member 188,as shown in FIG. 20C, may be provided to limit deflection of the secondarm portion 184 during insertion of the plunger rod 14 into the stopper12. This stop member 188 is positioned adjacent an outer surface 190 ofthe first arm portion 182 at a location adjacent to an inner surface 191of the second arm portion 184. Portions of the second arm portion 184may include a reinforcement material 189 as necessary. Additionally, thebottom surface 193 of the second arm member 184 may be flat or taperedas desired, depending upon the shape of the mating surface undercutportion 136 of the stopper 12.

These double deflecting arm portions 182, 184 can deflect from the baseof the front end of the plunger rod 14 and from the top of the armattached to the base of the front end geometry. During insertion, anormal load is exerted on the outside surface of the second arm portion184. When the pressure is exerted at the top or front portion 186 of thesecond arm portion 184, first arm portion 182 deflects inwardly. As thepressure moves down the surface of second arm portion 184, this secondarm portion 184 will begin to deflect. Deflection is greatest when botharm portions 182, 184 are at maximum deflection. During aspiration, acompressive and/or torsional load is exerted on the arm portions 182,184 and the first arm portion 182 will begin to deflect inwards whilesecond arm portion 184 digs into a stopper undercut surface, such asundercut surface 136, as shown in FIG. 3. Deflection, however, islimited by the contact between arm second arm portion 184 and the innersurface 132 of the wall of the stopper 12. As discussed above, a stopmember 188 may be provided for reducing stresses on the arm portions182, 184 by limiting the deflection of the arm portions 182, 184 wherenecessary, making deflection independent of the surface pressure duringinsertion and after the stop member 188 and second arm portion 184 arein contact with each other.

The FIGS. 20A-20C embodiment can also include an opening 192 in the headmember 140 and rim member 142. This opening 192 is defined by a circularsidewall 194 and a plurality of ribs 195 extending inwardly from thiscircular sidewall 194 toward the opening 192.

According to a fifth embodiment, as illustrated in FIGS. 21A-21F, theattachment portion, generally indicated as 200, of the plunger rod 14can include a deflecting arm 204 which can include a single circulardeflecting arm or a plurality of deflecting arms extending from thefront end 126 of the elongated member 124. This deflecting arm 204defines a space 206, and during attachment of the plunger rod 14 withinthe stopper 12, the deflecting arm 204 deflects inwardly toward thespace 206. When the deflecting arms 204 have reached maximum deflectionand are housed in the undercut space 134 on the inside of the stopper12, a slug 208 may be is inserted into this space 206 to support thedeflecting arm 204 and prevent it from collapsing and separating fromthe stopper during use of the syringe 10. According to one embodiment,as illustrated in FIGS. 21D-21E, the elongated member 124 includes ahollow portion 210 and the slug 208 is pre-molded within this hollowportion 210. After the attachment of the plunger rod 14 to the stopper12, an application force is applied within the hollow portion 210 toforce the slug 208 into the space 206. Alternatively, the slug 208 maybe separately molded and subsequently inserted.

Another aspect of the present invention is a new plunger body design asshown in FIGS. 22A-22B, 23A-23B, 24A-24B, and 25. The plunger rod 14 ispreferably made of a rigid thermoplastic material. This design, asdiscussed in detail below, consists of a hollow elongated plunger rodbody wherein the hollow portion is defined by a plurality oflongitudinally extending lobes and preferably an odd number of lobes areprovided. In traditional solid body four rib plunger designs, a user mayapply a side load during aspiration that may be normal to the edge of arib, causing minimal side loading deflection, or normal to the region inbetween the ribs, i.e., 45° from the rib, causing maximum side loadingdeflections. The present invention introduces a plunger body comprisingan elongated body portion 234 having a front end 236, a back end 238,and a sidewall portion 239 extending along a longitudinal axis betweenthe front end 236 and the back end 238. The sidewall portion 239comprises a plurality of longitudinally extending lobes 240 defining aninterior hollow portion 242. An attachment member 244 is secured to thefront end 236 and is adapted for attachment of the plunger rod 14 to thestopper 12. A cover member 246 is secured to the back end 238 of theelongated body portion 234 for covering the interior hollow portion 242and providing a thumb press area 248 for application of a force to theplunger rod 14 during use.

The longitudinally extending lobes 240 preferably comprise an odd numberof lobes spaced substantially equidistant with respect to one another.According to one embodiment, as shown in FIGS. 23A-23B, the plurality oflongitudinally extending lobes 240 comprises a three lobe design 250positioned at approximately 120° with respect to one another. Accordingto still another embodiment, as shown in FIGS. 22A-22B, the plurality ofextending lobes 240 number at five, forming a five lobe design 251wherein the lobes 240 are spaced substantially equidistant with respectto one another. The lobes are positioned with respect to one another toform substantially uniform side loading deflection of the plunger rod14. Providing an odd number of lobes 240 decreases the expecteddeflection when a load is applied to the region between the lobes 240 byintroducing a lobe on the opposite side which supports the reactionload. The present invention also includes four lobe 240 hollow elongatedplunger body designs 252, such as illustrated in FIGS. 24A-24B. Becausethe body portion of the plunger 14 includes a hollow portion 253, theadvantages associated with the hollow design, as discussed above, wouldalso be present in the four lobe design 252. The hollow design alsoprovides additional stiffness to the body portion 234 of the plunger rod14 and several ergonomic improvements, such as reduced product costs,easier manufacturing procedures, and the like as discussed in detailbelow.

The plunger rod 14 of the invention may be manufactured according to thefollowing processes. In a first process, the elongated body portion 234and the front end attachment member 244 are integrally molded from thesame material. The plunger rod 14 is designed to have an interior hollowportion 242 so that a core pin can be driven up the center of theplunger rod 14 during injection molding. This allows the plunger rod 14to be molded “standing up”, which results in a reduction in cycle timedue to additional cooling in the core pin and an increase in volume dueto an increase in cavity number. To cover the core pin opening orinterior hollow portion 242 on the thumb press side/area 248, asoft-touch surface disk 249 may be attached to the thumb press area 248for added comfort during injection.

According to a second process, as shown in FIG. 25, the plunger rod 14can be manufactured in three separate pieces. The attachment member 244can be injection molded, the elongated body portion 234 of the plungerrod 14 can be extruded or injection molded, and the cover member orthumb press disk 246 can be manufactured by a stamp molding process. Theattachment member 244, elongated body portion 234, and thumb press disk246 can be formed from different materials for improved performancewhere needed. For example, a more expensive material may be used to moldthe front attachment member 244 for improved performance and a softtouch elastomer may be used for the thumb press disk 246. Extruding thebody portion 234 of the plunger 14 allows for additional cross sectiongeometries that would provide uniform side loading deflection and allowfor ergonomic improvements that would other wise be limited by partinglines on the mold. Additionally, using an extrusion process for the bodyportion allows for the production of body portions of different lengthsfor use with different length syringe barrels 16 from a single extrusiondevice.

In the attachment arrangements of FIGS. 17A-17B, 18A-18B, 19A-19B, and20A-20C, each of these embodiments include a head member 140 having arim member 142 extending along a front surface 144 thereof wherein therim member includes a taper 196 adapted for contacting a correspondingtaper 198, within the stopper 12, as shown in FIG. 2B for applying aradial force to the stopper 12 upon the application of a forward forceto the plunger rod 14. In the FIG. 21A-21F arrangement, the deflectingarm 204 includes a taper 213 at a forward end 214 thereof adapted forcontacting a corresponding taper 198 within the stopper 12 for applyinga radial force to the stopper 12 upon the application of a forward forceto the plunger rod 14.

The stopper design of the present invention is intended to preventreflux by creating positive displacement of fluid into the attachedcatheter after the stopper 12 has been bottomed in the syringe barrel 16and force is released from the plunger rod 14. The features of thestopper 12 that act to create this positive displacement are the seal atthe nose portion 34 of the stopper 12, the flex or relative movement ofthe stopper 12 between the nose portion 34 and the forward or firstsealing rib 46, and a means by which potential energy in the form ofpressurized fluid can be captured and stored prior to the release of theforce from the plunger rod 14. The relative movement of the first rib 46with respect to the nose portion 34 of the stopper 12 is achieved bymeans of the flexible membrane 44 that connects the outer first rib 46to the flexible core member 32 and nose portion 34. The energy storingis achieved by means of both the flexible membrane 44 and the air bubbleor air pocket chamber 53 that is trapped under the folded forwardextending skirt 50 just forward of the first rib 46.

As illustrated in FIGS. 10-12, positive displacement or a method ofpreventing reflux within the syringe barrel includes the followingsteps. The first step provides a stopper 12 having a main body definingan open rearward end 28 and a closed front end 30. The open rearward end28 is adapted to receive a front forward end attachment member 31 of aplunger rod 14 therein. A flexible core member 32 is interconnected withthe main body 26 via a flexible membrane 44 integrally formed with themain body 26 adjacent the closed front end 30. The flexible core member32 includes a nose portion 34, preferably having a profile, as discussedabove, which is self-centering and adapted to create a positive sealwith an interior surface of the luer 20 of the syringe barrel 16. Themethod further includes the step of inserting the front forward endattachment member 31 of the plunger rod 14 within the open rearward end28 of the stopper 12. Applying a force to the plunger rod 14 to advancethe stopper 12 into the syringe barrel 16 until the nose portion 34 ofthe flexible core member 32 contacts the interior surface 36 of thesyringe barrel luer 20 forming a seal and trapping fluid from flowinginto the luer 20. Applying additional force to the plunger rod 14 tocompress the nose portion 34, advances the at least one rib 46 withinthe syringe barrel 16 and compresses the trapped air to form increasedpressure within the air pocket 53. The final step of the methodcomprises releasing the force on the plunger rod 14 to release the sealbetween the nose portion 34 and the interior surface 36 of the luer 20wherein friction force maintains the rib 46 in an advanced positionwithin the syringe barrel 16 such that the increased pressure within theair pocket 53 causes any trapped fluid to be pushed through the luer 20and any attached catheter.

FIGS. 2A-2B and 3 show a stopper design wherein the stopper 12 includesat least one forward extending skirt 50 extending from a closed frontend 30 of the main body 26 and wherein the step of applying a force toadvance the stopper 12 into the syringe barrel causes this skirt 50 todeflect inward with respect to the main body 26 of the stopper 12 tosubstantially contact, or to within a predetermined distance withrespect to an outer portion 52 thereof, to form an air pocket 53 fortrapping air therein. The step of applying additional force to theplunger rod 14 to compress the nose portion 34 causes the flexiblemembrane 44 to stretch. The step of releasing the force on the plungerrod 14, thereby releases the force on the flexible membrane 44, causingany trapped fluid to be pushed through an outlet opening or luer 20 andany attached catheter.

FIGS. 4A and 4B show a stopper design which does not rely on a flexibleskirt to trap an air bubble to assist in storing energy to force anytrapped fluid through the luer 20. Rather, this design only relies onthe flexibility of the membrane 44A connecting the flexible core member32 to the main body 26 of stopper 12 to capture pressure energy andreturn it once force is released from the plunger rod 14. Additionalfeatures that can trap an air bubble include other forms of molded-inpockets or slotted channels in the stopper face.

FIGS. 5A and 5B illustrate yet another design of the stopper 254,according to the invention. This design, discussed in detail above,shows a lip seal for sealing against the barrel. The front seal 256 ofthe stopper 254 is located on the leading edge of flexible arm 258. Theinitial sealing pressure is generated by the arm's interference with thebarrel wall. When the pressure in the syringe barrel 16 increases, anoutward radial force is applied to the inside 259 of the flexible arm258. This outward push will increase the force with which the sealpresses against the barrel wall.

A method of positively displacing fluid and preventing reflux within asyringe barrel utilizing the stopper design of FIG. 6C is also providedby the present invention and is illustrated in FIGS. 13-15. This methodcomprises the steps of providing a stopper 12 comprising a main body 26having a closed front end 30. The main body 26 may also include an openrearward end 28 which is adapted to receive a front forward endattachment member 31 of a plunger rod 14 therein. The main body 26includes a first body portion 60 having a first diameter and a secondbody portion 62 having a second diameter which is larger than the firstdiameter of the first body portion 60. A flexible core member 32 isintegrally formed with the main body 26 adjacent the closed front end30. The flexible core member 32 includes a nose portion 34 extendingfrom the front end, a shoulder 64 extending around the first bodyportion 60 of the main body 26, and at least one perimetrical skirt 66extending from the second body portion 62 toward the front end 30 of themain body 26. The perimetrical skirt 66 cooperates with the shoulder 64for trapping at least one air pocket/bubble 68 therein. The perimetricalskirt 66 includes a radially extending bump or first rib 77 along anouter surface lip portion 74. The method further comprises the steps ofproviding at least a second rib 88 extending radially outward around aperimeter of an outer diameter portion or second body portion 62 of themain body 26, inserting the front forward end attachment member 31 of aplunger rod 14 within the open rearward end 28 of the stopper 12,applying a force to the plunger rod 14 to advance the stopper 12 intothe syringe barrel 16 until the nose portion 34 of the flexible coremember 32 contacts the back or interior surface 36 of an outlet opening,such as a luer 20, forming a seal and trapping fluid from flowing intothe luer 20, applying additional force to the plunger rod 14 to compressthe nose portion 34, advancing the second rib 48 within the syringebarrel 16 and compressing the trapped air to form increased pressurewithin the air pocket 68. Upon completion of the flushing operation, themethod includes the step of releasing the force on the plunger rod 14 torelease the seal between the nose portion 34 and the interior surface 36of the luer 20 wherein friction force maintains the second rib 48 in anadvanced position within the syringe barrel 12 such that the increasedpressure within the air pocket 68 causes any trapped fluid to be pushedthrough the luer 20 and any attached catheter. When the seal is lost,the pressure and stored energy in the air pocket/bubble 68 is released.This air pocket/bubble 68 will expand forcing fluid out from in thefront of the stopper 12. This release of pressure pushes outward throughthe luer 20 causing fluid to be pushed out through any attachedcatheter.

The nose portion 34 of the flexible core member 32 has a profile adaptedto create a positive seal with the interior surface of the luer 20 ofthe syringe barrel 16. This core member 32 is interconnected with themain body 26 via a flexible and/or elastic membrane 44. The step ofapplying additional force to the plunger rod 14 to compress the noseportion 34 causes the flexible membrane 44 to stretch and the step ofreleasing the force on the plunger rod 14 releases this force on theflexible membrane 44 to cause any trapped fluid to be pushed through theluer 20 and any attached catheter preventing reflux within the syringebarrel 16.

The present invention has numerous advantages over existing plunger rodand stopper designs. In one aspect of the invention, reduced break-looseforces are present when the stopper 12 is first advanced which increasesthe ease of use of the device and reduce the release that occurs whenthe stopper 12 is first broken loose. The present designs also improveor reduce the sustaining forces on the stopper 12 due to reducedinterference between the stopper 12 and the syringe barrel 16 due to theactive seal, which allows the plunger rod 14 and stopper 12 assembly tobe used in a wider variety of syringe pump applications. Still anotheradvantage of the inventive assembly is the improved connection betweenthe plunger rod 14 and the stopper 12, especially when the stopper 12 isinserted into the syringe barrel 16 before the plunger rod 14 isattached to the stopper 12. Previous designs, which used a threadedconnection, tended to deform the stopper or push it off center,increasing the chance of leakage. Finally, the inventive design achievesa positive displacement of the fluid after the plunger rod 14 isbottomed and the force on the plunger rod 14 is released.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of invention which is to be given the fullbreadth of the claims appended and any and all equivalents thereof.

1. A plunger rod adapted for attachment with a stopper for use with asyringe barrel, said plunger rod comprising: (a) an elongated memberhaving a front end and a back end and extending along a longitudinalaxis; and (b) at least one deflecting arm associated with said front endof said elongated member, said deflecting arm capable of deflectingradially inward during insertion of said plunger rod into a stopper anddeflecting outward into contact with an inner surface of such stopperafter insertion into such stopper to lock said plunger rod within saidstopper.
 2. The plunger rod of claim 1, comprising at least twodeflecting arms.
 3. The plunger rod of claim 1, wherein said plunger rodfurther comprises at least a first stop member for limiting deflectionof said deflecting arm during insertion of said plunger rod into suchstopper.
 4. The plunger rod of claim 3, wherein said front end of saidelongated member comprises a head member extending from the front end,said head member including a rim member extending along a front surfacethereof.
 5. The plunger rod of claim 4, wherein said at least onedeflecting arm extends rearward from a bottom surface of said rimmember.
 6. The plunger rod of claim 5, wherein said first stop member ispositioned adjacent to a rearward portion of said head member.
 7. Theplunger rod of claim 4, wherein said at least one deflecting arm extendsfrom a center portion of said head member.
 8. The plunger rod of claim7, wherein said first stop member extends outward from a rearwardportion of said head member.
 9. The plunger rod of claim 8, wherein asecond stop member extends rearward from a bottom surface of said rimmember to limit arm deflection of said deflecting arm.
 10. The plungerrod of claim 4, wherein at least one deflecting arm extends rearwardlyfrom a bottom surface of said rim member.
 11. The plunger rod of claim10, wherein said first stop member extends outward from a rearwardportion of said head member.
 12. The plunger rod of claim 10, furthercomprising a second stop member extending downward from an outer edge ofsaid rim member to limit arm deflection of said deflecting arm.
 13. Theplunger rod of claim 1, wherein said front end of said elongated membercomprises a base member having a head member extending from a front end,said head member including a rim member extending along a front surfacethereof and wherein said at least one deflecting arm comprises a firstarm portion extending from said base member parallel with said headmember and a second arm portion attached to a front portion of saidfirst arm portion extending in a rearward and outward direction withrespect to said first arm portion.
 14. The plunger rod of claim 13,further comprising a stop member to limit deflection of said second armportion during insertion of said plunger rod into such stopper.
 15. Theplunger rod of claim 14, wherein said stop member is positioned adjacentan outer surface of said first arm portion at a location adjacent to aninner surface of said second arm portion.
 16. The plunger rod of claim1, wherein said front end of said elongated member comprises a headmember including a rim member extending along a front surface thereofand wherein said rim member is formed from a material capable of formingan active seal with an inside surface of such stopper.
 17. The plungerrod of claim 16, wherein said head member and said rim member include ahollow portion defined by at least one sidewall, said sidewall having aplurality of inwardly extending ribs extending toward the center of saidhollow portion for contacting such inside surface of such stopper. 18.The plunger rod of claim 1, wherein said front end of said elongatedmember comprises a head member extending from the front end, said headmember including a rim member extending along a front surface thereofand wherein said rim member includes a taper adapted for contacting acorresponding taper within such stopper for applying a radial force tosuch stopper upon the application of a forward force to said plungerrod.
 19. The plunger rod of claim 1, wherein said deflecting armcomprises one of at least two deflecting arms and a single circulardeflecting arm extending from said front end of said elongated member soas to define a space wherein upon insertion of said plunger rod intosuch stopper, a slug is inserted into said space to prevent one of saiddeflecting arms and said deflecting arm from collapsing duringaspiration of such syringe.
 20. The plunger rod of claim 19, whereinsaid elongated member is hollow and said slug is pre-molded within saidelongated member and an application force is applied within said hollowmember to force said slug into said space.
 21. The plunger rod of claim19, wherein said deflecting arm includes a taper at a forward endthereof adapted for contacting a corresponding taper within such stopperfor applying a radial force to such stopper upon the application of aforward force to said plunger rod.
 22. A plunger rod adapted forattachment with a stopper for use with a syringe barrel, said plungerrod comprising: (a) an elongated hollow member having a front end, aback end, and a sidewall portion extending along a longitudinal axisbetween said front end and said back end, said sidewall portioncomprising a plurality of longitudinally extending lobes defining aninterior hollow portion; (b) an attachment member secured to said frontend adapted for attachment of said plunger rod to such stopper; and (c)a cover member secured to said back end of said elongated member forcovering said hollow portion and providing a thumb press area forapplication of a force to the plunger rod during use.
 23. The plungerrod of claim 22, wherein said longitudinally extending lobes comprisesan odd number of lobes spaced substantially equidistant with respect toone another.
 24. The plunger rod of claim 22, wherein said plurality oflongitudinally extending lobes comprises three lobes positioned atapproximately 120° with respect to one another.
 25. The plunger rod ofclaim 22, wherein said plurality of lobes are positioned with respect toone another to form substantially uniform side loading deflection ofsaid plunger rod.
 26. The plunger rod of claim 22, wherein saidelongated member and said front end attachment member are integrallymolded from the same material.
 27. The plunger rod of claim 22, whereineach of said elongated member, said front end attachment member, andsaid back end cover member are formed separately from differentmaterials.
 28. A plunger rod and stopper assembly adapted for use with asyringe barrel, said assembly comprising: (a) a plunger rod having afront attachment end and a back end and extending along a longitudinalaxis; (b) at least one deflecting arm associated with said attachmentend of said elongated member, said deflecting arm adapted to deflectradially inward upon an application of force thereto and to deflectradially outward upon a release of such force; and (c) a stopper havinga main body defining an open rearward end and a closed front end, saidopen rearward end defined by an inside wall surface and an undercutportion, said open end adapted for receiving said front attachment endof said plunger rod such that said deflecting arm is deflected duringinsertion of said front attachment end and deflects outward afterinsertion to become trapped between at least a portion of said insidewall surface and said undercut portion to lock said plunger rod withinsaid stopper.
 29. The assembly of claim 28, wherein the front attachmentend of the plunger rod comprises a head member extending from the frontend, said head member including a rim member extending along a frontsurface thereof and wherein said rim member includes a taper adapted forcontacting a corresponding taper within such stopper for applying aradial force to such stopper upon the application of a forward force tosaid plunger rod.
 30. The assembly of claim 29, wherein thecorresponding taper of the stopper comprises a continually taperingsurface.